Synthesis, Characterization and Biological · 2019. 7. 31. · Synthesis, Characterization and...

ISSN: 0973-4945; CODEN ECJHAO

E-Journal of Chemistry

http://www.e-journals.net 2009, 6(3), 743-746

Synthesis, Characterization and Biological

Activity of Mn2+

, Co2+

, Ni2+

and Cu2+

Complexes of Benzoic Acid Ligand

T. ARUNACHALAM*, R. BHAKYARAJ

§ and A. K. SASI

Department of Chemistry, §Department of Microbiology,

J. J. College of Arts and Science, Pudukkotai, Tamilnadu, India.

[email protected]

Received 4 October 2008; Accepted 11 December 2008

Abstract: Metal complex of Mn(II), Co(II), Ni(II) and Cu(II) with benzoic acid

have been prepared and characterized by physiochemical methods. On the basis

of electronic spectra and magnetic susceptibility measurement in conjunction

with infrared spectra, six coordinated octahedral structure have been proposed to

all the complexes. The benzoic acid and their complexes have been tested for

their antibacterial activity against the bacteria E. coli, Bacillus subtilis,

Pseudomonas aeruginosa and Staphylococcus aureus. Further, the non

electrolytic nature of all the synthesized complexes was identified from

conductivity measurements.

Keywords: Benzoic acid ligand, Complexes, Biological activity.

Introduction

Coordination compounds have been a challenge to inorganic chemist since they were identified

in the 19th century. They defy the usual rules of valence at that time and hence called complexes.

They play vital role in our lives. Transitions metal complexes with soft or hard donor groups

have been used extensively in coordination and organometallic chemistry1. Reaction of

coordinated ligands model systems of biological interest, analytical chemistry, agriculture and

optical display devices2-4

. The earlier work exhibits metal with thiosemicarbazone as better

anticancer agent5-7

. There is currently a resurgency of interest in the biochemistry as well as

the coordination chemistry of bivalent Mn, Co, Ni and Cu due to their biological importance.

From literature, bivalent metal with Schiff base as ligands were extensively studied towards

antimicrobial activity. In view of this and our interest in biologically active coordination

compound, the present work communicating the synthesis, characterization and biological

activity of M2+

(M=Mn, Co, Ni, Cu) with benzoic acid as ligand.

744 T. ARUNACHALAM et al.

Experimental

All the chemicals and solvents used were analytical chemistry pure grade. Solvents were purified and dried according to the standard procedure. The ethanolic solution of ligands (Benzoic acid) and ethanolic solution of M(II) (Mn, Co, Ni, Cu) with 1:6 molar ratio were slowly mixed with constant stirring. The mixture was refluxed for 7 h using water condenser. The resulting solution was reduced to one third its volume and allowed to stand overnight at room temperature. The precipitated crystalline product was separated by using filtration, washed properly with ethanol and dry ether and dried over CaCl2 vaccuo. The solubility of all the complex prepared were checked using solvent DMSO, acetonitrile, water and ethanol. The conductivity of metal complexes was measured in DMSO medium (10 m molar) using Conductivity Bridge, Model Systronics type 304 and a dip type cell which in calibrated with KCl solution. The magnetic susceptibility and effective magnetic moment (BM) was calculated using Gouy balance (Model: KEYROY). Electronic spectra of all the complex were recorded in nujol mull using Shimadruz MPS-500 spectrophotometer at Alagappa University, Tamilnadu, India. The IR spectrum of complex in nujol mull (using Cesium iodide pellets) was recorded on a Perkin -Elmer 283 spectrophotometer in FTIR region.

Antimicrobial activities of the ligand and the complexes have been carried out against

the pathogenic bacteria like Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and

Pseudomonas aeruginosa, using nutrient agar medium by disc diffusion method8. The test

solution were prepared in DMSO and soaked in filter paper of 5 mm diameter and 1mm

thickness. These discs were placed on the already seeded plates and incubated at 35 oC for

24 h. The diameters (mm) of the inhibition zone around each disc were measured after 24

hours. Streptomycin was used as standard.

Results and Discussion

All the complexes are insoluble in water but soluble in DMSO and acetonitrile. The

solubility and stoichiometric composition are listed in Table 1. The electrolytic conductance

data in DMSO at the concentration10-3

molar suggest the non electrolytic nature of all

complexes. Further the absence of any color change in DMSO reveals us there in no

distortion in their geometry. The magnetic moment value for all the complexes corresponds

to high spin M(II) ion. The details are given in Table 2.

Table 1. Stoichometric composition and solubility of synthesized complexes.

Solubility Complexes

Mole of

metal ion

Mole of

ligand Water DMSO Acetonitrile

Mn L’6 0.03 0.1819 Insoluble Soluble Soluble Co L’6 0.02 0.1236 Insoluble Soluble Soluble

Cu L’6 0.035 0.2116 Insoluble Soluble Soluble

Ni L’6 0.025 0.1415 Insoluble Soluble Soluble L’- Benzoic acid

Table 2. Magnetic moment and conductivity.

Magnetic behavior Conductivity

Complex Mag. susceptibility,

cgs unit µeff(BM)

Conductance,

Ohm-1

Molar conductance,

Ohm-1

cm2 mol

-1

Mn L’6 0.0106 5.13 0.01x10-3

21.27

Co L’6 5.648x10-3

3.17 210x10-3

47.39

Ni L’6 1.059x10-3

1.613 11.7x10-6

24.38

Cu L’6 2.946x10-3

2.7 11.8x10-6

25.26

Synthesis, Characterization and Biological Activity of Complexes 745

The reflectance spectrum of Mn complexes with benzoic acid shows five bands. The weak

bands are due to d-d transition from high spin d5 configuration involving spin paring. Further there

is only one way of arranging five electrons with parallel spin in five orbitals, however there are

many ways if two of these electrons are paired. The broad band at 13333 cm-1

for Cu(II) complex

suggesting that are tetragonal type. The spin allowed transition of Co(II) complexes with benzoic

acid was identified at 25000 cm-1. A broad band for Ni(II) at 23000 cm

-1 confirm the octahedral

geometry. The absence any band below 1000 cm-1(10 Dq) eliminates the possibility of tetrahedral

environments. The characteristic band and its transitions are given in Table 3.

The IR spectra of the benzoic acid and the corresponding metal complexes have been

compared in order to fix the mode of bonding of the benzoic acid in the metal complexes.

The benzoic acid shows strong band at 1700 cm-1

-1630 cm-1

characteristic of (C=O)st

frequency. The IR spectrum of corresponding complexes this band is shifted to lower

frequency region 1510-1525 cm-1

.The broad band at 3513-3300 cm-1

is for (O-H)st frequency

in free ligand with the intramolecular hydrogen bonding and the same band appeared in the

complexes, indicating the absence of deprotonation of the benzoic acid group. The above

discussion confirm that the coordination through only (C=O) group, not through (O-H)

group. Absence of any band around 880 cm-1

indicating the absence of coordination by

atmospheric water. The details are shown in Table 3.

Table 3. Electronic and IR spectral data.

IR Frequency, cm-1

Absence of metal In complex Complex Electric spectra

cm-1

(C=O) st (O-H) st (C=O) st (O-H) st

Mn L’6 18900, 23100, 24970,

28000 & 29700

1700 3000 1510 3000

Co L’6 17250, 25000 &

35700

1700 3000 1510 3000

Ni L’6 23000 1700 3000 1510 3000

Cu L’6 13333 1700 3000 1510 3000

Antibacterial activity of ligand and corresponding complexes are recorded in Table 4. It

has been observed that the metal complex have a high activity than ligand against same

organisms under the identical experimental condition. The result show that the activity

enhances from Mn2+

to Cu2+

on charge density increases. This can be understood when

electrons are draining from metal to ligand by back donation will facilitate the

intramolecular hydrogen bonding between coordinated ligands and slowly approaching the

chelating character, which subsequently favor lipophilic nature of central metal ion in

permeation through the lipid layer of membrane8.

Table 4. Antimicrobial activity of compounds (Diameter of inhibition zone in mm and

concentration in ppm).

E. coli B. subtilis P. aeruginosa S. aureus Compound

500 1000 500 1000 500 1000 500 1000

Ligand 5.0 6.2 5.4 5.9 6.7 3.1 7.0 8.2

Mn L’6 9.0 10 8.0 9.0 10 11 10.5 12.0

Co L’6 10.2 12 9.1 10.5 11 12.6 11.7 16.5

Cu L’6 11.0 13.8 10.2 12.1 12.1 13.9 12.2 15.4

Ni L’6 12.0 14.6 11.5 13.5 13.2 15.2 13.5 16.2

Standard 22 24 24.2 26.5 20.1 22.3 22.0 23.5

746 T. ARUNACHALAM et al.

Conclusion

All the complexes are octahedral geometry and paramagnetic nature. They show remarkable

activity against all the organism tested. The mode of action of complexes may involve the

formation of hydrogen bonds involving the benzoic acid group with microbial or ribosome

of the microbial cells resulting in interference with normal cell process. The toxicity

increases with increasing concentration of the complexes.

References

1. Sarkar A R and Mandal S, Synth React Inorg Met-Org Chem., 2000, 80, 1477.

2. Mishra A P and Khare M, Indian J Chem Soc., 2000, 77, 367.

3. Siddiqui R S and Nishat N, Synth React Inorg Met-Org Chem., 2000, 30,1005.

4. Maurya M R and Bharatia N, Transition Met Chem., 1993, 23, 5.

5. Subezynski W K, Anholine W E, Hyde J E and Petering O H, J Am Chem Soc., 1987,

109, 46.

6. Murugkar A, Unnikrishnan S B, Padhye S, Treat Triantafullan E and Sinn E, Metal

Based Drugs, 1999, 6, 177.

7. Agarwal K C and Santorelli A C, Prog Med Chem., 1978, 15, 351.

8. Tweedy B G, Phytopathology, 1964, 55, 910.

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